This invention relates to a method for improving the utilization of high molecular weight polyelectrolytes in the dewatering of aqueous suspensions; the method reduces the amount of polyelectrolyte required to effectively dewater an aqueous suspension and thereby provides a significant reduction of the costs of the polyelectrolyte necessary to effectively dewater an aqueous suspension. More particularly, the polyelectrolyte required to effectively dewater an an aqueous suspension may be reduced to as little as one-half of that required using conventional techniques.
As a general practice, high molecular weight polyelectrolytes are mixed and used shortly therafter or only after moderate mixing, holding or aging periods in the neighborhood of 30-45 minutes. Metered amounts of the polyelectrolyte are then continuously fed to a flow of an aqueous suspension in the dewatering process. For example, the smaller municipal wastewater treatment plants where polyelectrolyte solution requirements per filter may be of the order of 500-600 gallons of 0.001 parts by weight of polyelectrolyte solution per filter per run, the polyelectrolyte is mixed immediately prior to use in a single tank. Larger installations with greater requirements may use a continuous mixer in which "aging" (holding) times for the mixed polyelectrolyte may range from a few minutes up to about an hour. Typically, polyelectrolyte dosage is based on experience obtained using the solution mixed in the plant.